Setting and binding material from natural mineral anhydrite



Patented Aug. 5, 1952 SETTING AN D :BINDING' MATERIAL FRI OM NATURALNHNERADANHYDRITE Herman WebeniHarriman, Tenn.

No Drawing. Application April 34195 I SerialNo.'153;157"

This is a continuation-impart of my patent application Ser. No. 83,519;filed March25,11949.

'This invention 'relatesto a non-hydrating'setting and binding materialand to a process of manufacturing the same. More particularly, theinvention relates to a quick setting, non-hydrating composition ofmatter made from the natural mineral, anhydrous calcium sulphate, oranhy, drite. Anhydrite, in its natural state, though finely ground, isincapable of hydrating and setting so as to form a solid cast or bodyafter being mixed with water and allowed to dry. Numerous attempts havebeen made to treat anhydrite so as to enable it to hydrate and to usesuch anhydrite for the manufacture of plaster or other materials capableof setting when mixed with water. Such previous attempts have not beencommercially successful.

It is an object of this invention to provide a non-hydrating compositionof matter made from natural anhydrite capable of setting quickly into ahard, dense mass, if treated with water.

Another object is to provide a method of treating anhydrite so as toproduce a non-hydrating, cementitious material capable of setting andforming masses having relatively higher compressive and tensile strengthand greater hardness than other hydrating, cementitious materialscontaining calcium sulphate, e. g., calcined gypsum (CBISOF /zHZO).

A further object of this invention is to provide a non-hydratingcomposition of matter, which utilizes the mineral anhydrite in such amanner that a minimum of treatment and handling of the material will benecessary.

Other objects and characteristics of the process and products, accordingto my invention, will become apparent from the following descriptionthereof.

I have found that a small amount (3-5%) of slaked lime (Ca(OH)2) mixedwith the starting material, ground to pass 1'75 mesh screen, produces abasic medium which causes a rapid solution and supersaturation of theanhydrite in the mixing water, resulting, with the evaporation of thewater, in a vigorous recrystallization back to the anhydrite, the causeof binding and setting. No hydration of the anhydrite is intended, nordoes it occur. This recrystallization is also the reason that thehardness, compression resistance and tensile strength obtained exceed byfar the corresponding values for hydrated gypsum plasters.

No other treatment of the starting material is necessary to produceproducts which set per- 2 Claims. (01. 106409) *fectlywithout:hydrating, nor will: it be: necessary to add *metallic salts-or--sulphates as accelerators to theraw material.

The advantages afforded by this new, nonhydrating setting and bindingmaterial of this anhydrite type are apparent from the following examplesof products prepared from the same.

Example 1.-As a neat mixture usable for inside work in such form assolid, weight-bearing partition blocks, bricks, plates and floors, andas finish coat plaster, etc.:

Byweight:

, parts ground anhydrite passing 175 mesh screen (5% Ca(OHl;)

mortar (1:1):

By weight:

100 Gparts ground anhydrite passing 175 mesh (5% slaked lime a(OH)2) 100parts fine sand 40 parts water Pounds Per Square Inch After- 7 days 28days Compression Resistance 1100+ 1500+ Tensile Strength 200+ 250+Example 3.-For use as second coat plaster or mortar (1:2):

By weight:

100 parts ground anhydrite passing 175 mesh 5% slnked lime (Ca(OH)n) 200parts fine sand 45 parts water Pounds Per Square Inch After- 7 days 28days Compression Resistance 600+ 1200+ Tensile Strength 80+ Example4.For use as base coat plaster or mortar (1:3):

By weight: l

100 (parts ground anhydrite passing 175 mesh 5% slaked lime 300 partsfine sand Any inorganic material such as rock wool, glass fiber,vermiculite, cinders, etc., can be added for special purposes; alsoorganic materials after mineralizing same with sodium silicate.

I claim: 1. A process of manufacturing an anhydrous setting and bindingmaterial from natural anhydrite by recrystallization of the startingmaterial in a basic medium. which consists in grinding the startingmaterial to pass 175 mesh screen, mixing it with 3-5% calcium hydroxide,mixing the resulting material with water, whereby a rapid solution andsupersaturation of the anhydrite is performed in the watery solution.and recrystallizing the anhydrite by evaporation of water.

2. A new anhydrous, quick etting composition of matter consisting ofmineral anhydrite ground to pass 1'75 mesh screen and 3-5% slaked limewhich in the presence of water yields a basic medium.

HERMAN WEBER.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,470,731 Hartner Oct. 16. 19231,972,527 Lefebure Sept. 4. 1934

1. A PROCESS OF MANUFACTURING AN ANHYDROUS SETTING AND BINDING MATERIALFROM NATURAL ANHYDRITE BY RECRYSTALIZATION OF THE STARTING MATERIAL IN ABASIC MEDIUM, WHICH CONSIST IN GRINDING THE STARTING MATERIAL TO PASS175 MESH SCREEN, MIXING IT WITH 3-5% CALCIUM HYDROXIDE, MIXING THERESULTING MATERIAL WITH WATER, WHEREBY A RAPID SOLUTION ANDSUPERSATURATION OF THE ANHYDRITE IS PERFORMED IN THE WATERY SOLUTION,AND RECRYSTALLIZING THE ANHYDRITE BY EVAPORATION OF WATER